Magnetic triode



Sept 11, 1956 A. M. cLoGsToN 2,762,944

MAGNETIC TRIODE Filed Oct. 50, 1945 FIGLIv ANODE VOLTAGE= 500 VOLTS 0- ANODE CURRENT (MILLIAMPERES) GRID CURRENT GRID CURRENT ANODE CURRENT (MILLIAMPERES) N A l I I l 200 400 600 BOO IOOO GRI D VOLTAGE INVENTOR ALBERT M. CLOGSTON MLQLM ATTORNEY United States Patent O MAGNETIC TRIoDE Albert M. Clogston, Melrose, Mass., assignor, by mesne assignments, to the United States of America as represented by the Secretary of the Navy Application October 30, 1945, Serial N o. 625,666

`1 Claim. (Cl. 313-159) This invention relates to electron discharge devices and more particularly to three element electron discharge devices utilizing a magnetic field to prevent the ow of electrons to the grid or controlling element.

It is an object of this invention to provide a novel and improved electron discharge device having high anode current capacity for application in current amplification and switching circuits.

It is a further object of this invention to provide a novel and improved electron discharge device in which there shall be no danger of grid burn out or of secondary emission from the grid.

Other and further objects will appear during the course of the following description taken with the accompanying drawings in which:

Figs. 1 and 3 are sectional views of embodiments of this invention; and

Fig. 2 is a graph of certain electrical relationships existing in the embodiment of Fig. 1.

The embodiment in Fig. 1 comprises a cylindrical cathode 10, which is hollow to permit insertion of a heater and which is surrounded by a cylindrical metallic shell 11 which shall be referred to as the grid because of its controlling function, and an anode 12 in the shape of a disc having its center on the axis of the cathode and grid cylinder but spaced therefrom along said axis. Surrounding the cathode and grid to form an enclosure therefor in conjunction With the anode is a metallic envelope 13 to insure maintenance of the necessary high vacuum and through which connections are made to the enclosed elements in any suitable and well known manner, A magnetic field, represented by the arrow at H, is applied through the triode in a direction along the axis of the cathode and grid cylinder by permanent magnet 14.

Electrons emitted by cathode which is heated in any well known manner, are attracted towards grid 11 which is at a high positive potential with respect to the cathode. The electrons are forced to move in a spiral path around the cathode by the axial magnetic field and are thus prevented from striking the grid. Instead, because of space charge repulsion due to the high charge density in the cathode grid space, and the attraction of anode 12, which is also at a high positive potential with respect to the cathode, the electrons describe a helical path around the cathode and ilow to the anode. The density of the flow of electrons to the anode and, hence, the anode current, depends upon the potential of the grid as well as upon the potential of the anode. Normally the grid of this magnetic triode is maintained at a higher positive potential than the anode, but the current that ows to the grid is low since few electrons strike the grid.

Fig. 2 is a graph of the relationship between grid potential and the resulting anode and grid currents. By reference to that ligure it is noted that with an anode potential of 500 volts, a grid potential of 900 volts produces an anode current of 99 milliamperes, while the grid current is only ve milliamperes. It can thus be seen that current and power amplication is effected by the tube.

Another embodiment of this invention, shown in cross section in Fig. 3, consists of a double-ended magnetic triode which has two anodes 12a and 12b, one at each end of copper cylindrical grid shell 11, and axially aligned with cylindrical cathode 10. The axial magnetic field, represented by the arrow at H, is applied from the yoke of a permanent magnet through iron pole pieces 14a and 14b. The anodes are supported by glass insulators 15a and 15b.

Operation is the same as in the first embodiment except that electrons from cathode 10 which tend to flow in either direction will be collected at an anode. The current capacity is thus increased. This embodiment illustrates a particular advantage of the invention in that the grid shell can be an easily-cooled external wall allowing large power dissipation.

The invention is only to be limited by theappended claim.

What is claimed is:

An electron discharge device comprising, a cylindrical control electrode having an opening therethrough, a cathode positioned interiorly of said control electrode, a magnet, the pole pieces of said magnet each having a central aperture, said control electrode being interposed between said pole pieces and contiguous to the adjacent faces thereof, two anodes, each anode being positioned in the central aperture of a different one of said pole pieces, each said anode presenting a face proximate to a different end of said control electrode, insulative sealing means, said sealing means, pole pieces, and control electrode forming an evacuated inclosure, and electrical conductors connected to said cathode and anodes projecting through said sealing means.

References Cited in the tile of this patent UNITED STATES PATENTS 1,114,697 Hull Oct. 20, 1914 1,564,852 Hull Dec. 8, 1925 2,238,272 Linder Apr. 15, 1941 2,324,772 Gibson July 20, 1943 2,348,986 Linder May 16, 1944 2,404,212 Bondley July 16, 1946 

